There has been proposed a related art technique for detecting presence or absence of attachment of a cell. For example, JP-A-08-095678 discloses a technique using a switch that is mechanically switched to an on/off state by attaching/detaching the cell so as to detect whether or not a chargeable secondary cell is attached by on/off of the switch. Then, JP-A-08-095678 uses a remaining amount detecting unit for detecting, remaining amount of the cell so as to detect whether or not an unchargeable primary cell is attached by detecting whether or not the remaining amount of the cell exceeds a predetermined amount or more. Accordingly, JP-A-08-095678 detects the presence or absence of attachment of the cell.